There are many situations where, for diagnostic purposes, for monitoring purposes during surgery or other medical procedures, for treatment, or for other purposes, doctors or other medical personnel need to sense various body potentials and in particular potentials in the heart area. Such potentials are normally sensed by placing an electrode in contact with or adjacent to the area being monitored and connecting the electrode through a wire to a terminal. Typically, a number of electrodes are mounted to a sensing probe or are bundled into a catheter, each electrode being connected by a separate wire to a separate connector element. The connector element may be, for example, a plug or a pin of a multi-pin connector.
The manufacture and assembly of such sensing devices has heretofore been a very labor-intensive operation and therefore quite costly. The discrete wires are soldered, welded or brazed to the electrodes and assembled into catheter shafts, fabric, mesh or rigid bodies. The manufacture and assembly of such sensing devices thus involves a large number of assembly steps, many of which require skilled and often artistic human execution. In addition to high cost, the large number of hand-performed steps can also result in small nonuniformities in finished products which can cause potentially catastrophic medical errors if such nonuniformities are not picked up during final testing. The requirements for numerous, sometimes difficult hand steps in the assembly operation of a single sensing device can also result in a significant scrap rate during manufacturing.
Further, since each discrete wire in such sensing devices normally has separate insulation, the size of the sensing devices and their mechanical characteristics such as stiffness, are directly affected by the number of sensing electrodes in the probe. Since such sensing devices are frequently catheters which are introduced into the heart through an artery, the size limitations imposed by the wires limits the number of sensing electrodes which can be utilized. Typically, such catheters cannot have more than four to six electrodes. Current construction techniques for the sensing devices limit the available spacing between electrodes so that it is difficult to manufacture a catheter which can simultaneously measure the potentials at closely adjacent points on the heart.
Another problem with the existing biopotential sensing catheters is that the size of the wires results in the wires taking up the full available space in the artery for the catheter. Thus, it is not possible to include a lumen with the catheter. A lumen is desirable with a catheter for the introduction of radio-opaque dyes to assist in guiding the catheter or for the introduction of medication or other substances useful in connection with a particular medical procedure.
The high manufacturing costs of existing sensing devices results in their being relatively expensive to purchase. However, in order to avoid contamination and to avoid using a catheter or other sensing device which has been damaged either in use or in sterilization, such devices are normally marketed as disposable devices adapted for only a single use. Nevertheless, in an effort to reduce expenses, hospitals frequently attempt to sterilize and reuse such devices. Such a practice poses a serious risk of contamination to the patient and of inaccurate readings as a result of using a sensing device which has been damaged. However, so long as such devices continues to be expensive, they will tend to be reused.
In an effort to reduce both the size and cost of such sensing devices, it has been proposed that printed circuit technology be utilized in their manufacture. Heretofore, some printed circuit sensors have been utilized for measuring skin potentials and other potentials on the body surface, and for measuring certain brain potentials or other potentials near the surface. Techniques have not been developed for utilizing such technology in connection with percutaneous catheters where the usable length of the catheter may be in the range of 125 centimeters, or with other sensing devices adapted for use in the heart or other deep internal organs where the connection between the electrodes and the connector terminals is relatively long.
It is therefore an object of this invention to provide biopotential sensing devices which are substantially less expensive to manufacture and assemble than existing such devices.
A further object of this invention is to provide biopotential sensing devices which take up far less space than existing such devices, permitting a greater number of contacts to be utilized, permitting such contacts to be closer together, and permitting a lumen to be utilized in conjunction with such devices when used as a percutaneous catheter.
A more specific object of this invention is to provide percutaneous catheters and other sensing devices designed for endocardial or other use deep in the body which are inexpensive enough to manufacture and assemble that hospitals will be willing to dispose of such devices after a single use rather than attempting to sterilize and reuse them.
A still more specific object of this invention is to provide biopotential sensing devices, and in particular percutaneous catheters and other endocardial sensing devices, or sensing devices for other deep body applications utilizing printed circuit technology.